JP2602142B2 - Method for manufacturing semiconductor device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device,
In particular, the present invention relates to a method for manufacturing a semiconductor device having a twin well including a P-type well region and an N-type well region and a stopper region. 2. Description of the Related Art FIG. 1 shows a conventional method for manufacturing a twin well and a stopper region. In FIG. 1A, a silicon oxide film 2 is formed on a silicon substrate 1, a window for forming an N-type well region is opened, and a resist 3 is used as a mask.
An N-type well region is formed by ion implantation. Next, after removing the resist 3, a silicon oxide film 5 is formed on the entire surface as shown in FIG. Similarly to the method of forming the N-type well region , the silicon oxide film 6 and the resist 7 are masked.
As shown in FIG. 1C, a P-type well region is formed .
Thereafter, a silicon oxide film 9 is formed on the entire surface as shown in FIG. Finally, a window for forming a P-type stopper region is opened in the silicon oxide film 9 , and the P-type stopper region 12 is formed using the silicon oxide film 10 and the resist 11 as a mask as shown in FIG. I do. Therefore, when forming the P-type and N-type well regions, the P-type and N-type well regions must be formed with a margin in consideration of a mask shift.
Because of the margin at the boundary between the two regions, there is a limit in achieving high integration. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is directed to a semiconductor device having an N-type well region, a P-type well region and a P-type stopper region formed on a silicon substrate. In the manufacturing method, the density of the well region formed on the silicon substrate can be increased,
It is an object of the present invention to manufacture a semiconductor device that does not lower the impurity concentration when forming a selective oxide film. According to the present invention, there is provided a method of manufacturing a semiconductor device in which an N-type well region, a P-type well region and a P-type stopper region are formed on a silicon substrate. Selectively forming an oxidation-resistant film having a masking action, and forming the N-type well region by introducing N-type ions into the silicon substrate using the region where the oxidation-resistant film is formed as a mask. A step of selectively oxidizing the N-type well region using the oxidation-resistant film as a mask and forming a selective oxide film on the N-type well region so that the surface of the N-type well region is gentle from the boundary of the region; A step of continuing with an inclination, a step of removing the oxidation-resistant film by etching, and a step of forming P-type ions in the silicon substrate using the selective oxidation film as a mask. Forming the P-type well region adjacent to the N-type well region by introducing the P-type stopper region from the boundary between the P-type well region and the N-type well region to the P-type well region. And a step of forming According to the present invention, in a method of manufacturing a semiconductor device in which an N-type well region, a P-type well region and a P-type stopper region are formed on a silicon substrate, a boundary between the N-type well region and the P-type well region is adjacent to each other. With this arrangement, wells can be formed at a high density, and a highly integrated semiconductor device can be realized. Further, it is known that when an oxide film is formed by thermally oxidizing the surface of a silicon substrate into which impurity ions are introduced, P-type ions are more likely to segregate in the oxide film than N-type ions. .
According to the present invention, by forming the N-type well region first and forming the selective oxide film on the N-type well region, N-type ions introduced for forming the well are segregated in the selective oxide film. Since it is difficult, the impurity concentration does not decrease. FIG. 2 is a process chart for explaining one embodiment of a method of manufacturing a semiconductor device according to the present invention. In the figure, 13 is a silicon substrate, 14, 18, 19, 21 and 23 are silicon oxide films, 15 is a silicon nitride film, 16 and 22 are resists, 17 is an N-type well region, 20 is a P-type well region,
4 is a P-type stopper region. 2A, a silicon oxide film 14 and a silicon nitride film 1 are formed on a silicon substrate 13.
After forming 5, a window for forming an N-type well region is opened by photoetching, and an N-type well region 17 is formed by implanting N-type ions using the silicon nitride film 15 and the resist 16 as a mask. After the resist 16 is removed, selective oxidation is performed using the silicon nitride film 15 as a mask, and a silicon oxide film 18 is formed on the N-type well region 17 in FIG. Due to the formation of the silicon oxide film 18, the surface of the N-type well region 17 has a shape that continues with a gentle slope from the boundary of the region. Next, as shown in FIG. 2C, when the silicon nitride film 15 is removed and the silicon oxide film 14 thereunder is removed by etching, most of the silicon oxide film 19 remains in the selectively oxidized portion. Next, a P-type well region 20 is formed adjacent to the N-type well region 17 by implanting P-type ions using the remaining silicon oxide film 19 as a mask. Further FIG.
After a silicon oxide film 21 is formed on the entire surface as shown in FIG. 2D, a window for forming a P-type stopper is opened as shown in FIG. 2E, and a P-type stopper is formed using the resist 22 and the silicon oxide film 23 as a mask. An area 24 is formed. As is apparent from the above description, according to the present invention, in a method of manufacturing a semiconductor device for forming an N-type well region, a P-type well region and a P-type stopper region on a silicon substrate, There is an effect that the density of the well region formed on the silicon substrate can be increased. Further, by forming a selective oxide film on the N-type well region, segregation of impurity ions introduced into the silicon substrate into the oxide film can be reduced, and it is not necessary to reduce the impurity concentration. effective. [0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a conventional method for forming a stopper region. FIG. 2 illustrates a method for forming a stopper region according to the present invention. [Description of Signs] 13 ... Silicon substrates 14, 18, 19, 21, 23 ... Silicon oxide film 15 ... Silicon nitride films 16, 22 ... Resist 17 ... N-type well region 20 ... P-type well region 24 ... P-type stopper region

Claims (1)

(57) [Claims] N-type well region, P
In a method of manufacturing a semiconductor device in which a mold well region and a stopper region are formed, a step of selectively forming an oxidation resistant film having a masking action against oxidation on the silicon substrate; Forming the N-type well region by introducing N-type ions into the silicon substrate, selectively oxidizing the N-type well region using the oxidation-resistant film as a mask, and selecting the N-type well region on the N-type well region. Forming an oxide film, removing the oxidation-resistant film by etching, and introducing P-type ions into the silicon substrate using the selective oxidation film as a mask, thereby forming the P-type ions adjacent to the N-type well region. Forming a well region, forming a P-type stopper region from a boundary between the P-type well region and the N-type well region to the P-type well region. The method of manufacturing a semiconductor device characterized by comprising the step of forming.